In recent years, a technique to restore an image before degradation (hereinafter, referred to as a restored image) from a degraded image which has been degraded by the characteristics of the lens such as aberration in an imaging apparatus have been devised. As this technique, there is a method in which the lens-specific degradation information is stored up in advance, and a correction data corresponding to the object distance or focal length is created on the basis of the degradation information, and a restored image is generated from a degraded image on the basis of the correction data (for example, see Patent Document 1).
However, when the lens-specific degradation information, the object distance, the focal length or the like is unknown, it is difficult to use such a technique. Further, in this technique, the restoration accuracy reduces when different degradation has occurred in the degraded image from the degradation according to the premeasured information having been stored up, due to a production error of the lens and others. Further, in the case of generating a restored image from a degraded image that has been captured by the interchangeable lens imaging apparatus, since the assumed number of lenses is large, the amount of degradation information stored in advance becomes large.
Therefore, a technique called a blind deconvolution (blind deconvolution) of performing restoration by calculating degradation information from a degraded image has been devised, rather than by measuring and storing the degradation information in advance. The blind deconvolution is a technique of generating a restored image by estimation of a point spread function (PSF) as degradation information from the degraded image and by deconvolution of the point spread function with respect to the degraded image (for example, see Patent Document 2 and Non-Patent Document 1).